As we all come in through the vena cavae, we first enter into the right atrium. It's a homecoming party because we're returning from all parts of the body. Those of us that were down to the big toe meet up again with those that travelled to the left ear lobe and oh, the stories to share!
The sinoatrial (SA) node, located in the wall of the right atrium, stimulates the contraction of the atrium. This pushes everyone on through the tricuspid atrioventricular (AV) valve and on to the right ventricle.
(A side note - it's called tricuspid because it's made up of three cusps or flaps.)
